From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1755715AbeDVPG6 (ORCPT ); Sun, 22 Apr 2018 11:06:58 -0400 Received: from mx0b-001b2d01.pphosted.com ([148.163.158.5]:44420 "EHLO mx0a-001b2d01.pphosted.com" rhost-flags-OK-OK-OK-FAIL) by vger.kernel.org with ESMTP id S1753836AbeDVPGu (ORCPT ); Sun, 22 Apr 2018 11:06:50 -0400 Subject: Re: [PATCH] KVM: s390: reset crypto attributes for all vcpus To: David Hildenbrand , linux-s390@vger.kernel.org, linux-kernel@vger.kernel.org, kvm@vger.kernel.org Cc: borntraeger@de.ibm.com, cohuck@redhat.com, pmorel@linux.vnet.ibm.com, pasic@linux.vnet.ibm.com, pbonzini@redhat.com, rkrcmar@redhat.com References: <1524172432-26211-1-git-send-email-akrowiak@linux.vnet.ibm.com> From: Tony Krowiak Date: Sun, 22 Apr 2018 11:06:43 -0400 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:52.0) Gecko/20100101 Thunderbird/52.2.0 MIME-Version: 1.0 In-Reply-To: Content-Type: text/plain; charset=utf-8; format=flowed Content-Transfer-Encoding: 7bit Content-Language: en-US X-TM-AS-GCONF: 00 x-cbid: 18042215-0048-0000-0000-000002613FD3 X-IBM-SpamModules-Scores: X-IBM-SpamModules-Versions: BY=3.00008900; HX=3.00000241; KW=3.00000007; PH=3.00000004; SC=3.00000257; SDB=6.01021660; UDB=6.00521399; IPR=6.00800895; MB=3.00020714; MTD=3.00000008; XFM=3.00000015; UTC=2018-04-22 15:06:47 X-IBM-AV-DETECTION: SAVI=unused REMOTE=unused XFE=unused x-cbparentid: 18042215-0049-0000-0000-000044DE1F9A Message-Id: X-Proofpoint-Virus-Version: vendor=fsecure engine=2.50.10434:,, definitions=2018-04-22_04:,, signatures=0 X-Proofpoint-Spam-Details: rule=outbound_notspam policy=outbound score=0 priorityscore=1501 malwarescore=0 suspectscore=0 phishscore=0 bulkscore=0 spamscore=0 clxscore=1011 lowpriorityscore=0 impostorscore=0 adultscore=0 classifier=spam adjust=0 reason=mlx scancount=1 engine=8.0.1-1709140000 definitions=main-1804220170 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 04/20/2018 08:26 AM, David Hildenbrand wrote: > On 19.04.2018 23:13, Tony Krowiak wrote: >> Introduces a new function to reset the crypto attributes for all >> vcpus whether they are running or not. Each vcpu in KVM will >> be removed from SIE prior to resetting the crypto attributes in its >> SIE state description. After all vcpus have had their crypto attributes >> reset the vcpus will be restored to SIE. >> >> This function is incorporated into the kvm_s390_vm_set_crypto(kvm) >> function to fix a reported issue whereby the crypto key wrapping >> attributes could potentially get out of synch for running vcpus. >> >> Reported-by: Halil Pasic > A reported-by for a code refactoring is strange. I was asked to include this. > >> Signed-off-by: Tony Krowiak >> --- >> arch/s390/kvm/kvm-s390.c | 18 ++++++++++++++---- >> arch/s390/kvm/kvm-s390.h | 13 +++++++++++++ >> 2 files changed, 27 insertions(+), 4 deletions(-) >> >> diff --git a/arch/s390/kvm/kvm-s390.c b/arch/s390/kvm/kvm-s390.c >> index fa355a6..4fa3037 100644 >> --- a/arch/s390/kvm/kvm-s390.c >> +++ b/arch/s390/kvm/kvm-s390.c >> @@ -789,6 +789,19 @@ static int kvm_s390_set_mem_control(struct kvm *kvm, struct kvm_device_attr *att >> return ret; >> } >> >> +void kvm_s390_vcpu_crypto_reset_all(struct kvm *kvm) >> + { >> + int i; >> + struct kvm_vcpu *vcpu; >> + >> + kvm_s390_vcpu_block_all(kvm); >> + >> + kvm_for_each_vcpu(i, vcpu, kvm) >> + kvm_s390_vcpu_crypto_setup(vcpu); >> + >> + kvm_s390_vcpu_unblock_all(kvm); > This code has to be protected by kvm->lock. Can that be guaranteed by > the caller? I can hold the kvm->lock in this function, but if you look at the function from which it is called, kvm_s390_vm_set_crypto(vcpu) below, the kvm->lock is already held by that function to do other work. I suppose the kvm_s390_vm_set_crypto(vcpu) instruction could have released the lock prior to calling kvm_s390_vcpu_crypto_reset_all(kvm), but since this function is called within a block of crypto work, it made sense to me to place the responsibility for locking in the caller and include a comment in the comments for the function definition: Note: The kvm->lock must be held while calling this function > >> +} >> + >> static void kvm_s390_vcpu_crypto_setup(struct kvm_vcpu *vcpu); >> >> static int kvm_s390_vm_set_crypto(struct kvm *kvm, struct kvm_device_attr *attr) >> @@ -832,10 +845,7 @@ static int kvm_s390_vm_set_crypto(struct kvm *kvm, struct kvm_device_attr *attr) >> return -ENXIO; >> } >> >> - kvm_for_each_vcpu(i, vcpu, kvm) { >> - kvm_s390_vcpu_crypto_setup(vcpu); >> - exit_sie(vcpu); >> - } >> + kvm_s390_vcpu_crypto_reset_all(kvm); >> mutex_unlock(&kvm->lock); >> return 0; >> } >> diff --git a/arch/s390/kvm/kvm-s390.h b/arch/s390/kvm/kvm-s390.h >> index 1b5621f..981e3ba 100644 >> --- a/arch/s390/kvm/kvm-s390.h >> +++ b/arch/s390/kvm/kvm-s390.h >> @@ -410,4 +410,17 @@ static inline int kvm_s390_use_sca_entries(void) >> } >> void kvm_s390_reinject_machine_check(struct kvm_vcpu *vcpu, >> struct mcck_volatile_info *mcck_info); >> + >> +/** >> + * kvm_s390_vcpu_crypto_reset_all >> + * >> + * Reset the crypto attributes for each vcpu. This can be done while the vcpus >> + * are running as each vcpu will be removed from SIE before resetting the crypt >> + * attributes and restored to SIE afterward. >> + * >> + * Note: The kvm->lock must be held while calling this function >> + * >> + * @kvm: the KVM guest >> + */ >> +void kvm_s390_vcpu_crypto_reset_all(struct kvm *kvm); >> #endif >> >